The von Willebrand Factor-cleaving protease is involved in the limitation of platelet thrombus growth by proteolytic cleavage of von Willebrand Factor multimers in man (Furlan et al., Blood 1996, 87: 4223-4234). Recently, the molecular structure of von Willebrand Factor-cleaving protease and the corresponding gene have been described (WO 02/42441; Zheng et al., J. Biol. Chem. 2001, 276: 41059-41063).
A deficiency of von Willebrand Factor-cleaving protease could cause severe disorders such as acquired thrombotic thrombocytopenic purpura or hemolytic-uremic syndrome. One reason for such a deficiency of von Willebrand Factor-cleaving protease is the occurrence of autoantibodies which inhibit the von Willebrand Factor-cleaving protease (Furlan et al., Blood 1998, 91: 2839-2846; Furlan et al., N Engl J Med 1998, 339: 1578-1584). So far, such autoantibodies can be removed from a patient's plasma by protein A immunadsorption. However, the main disadvantage of protein A immunadsorption is its low selectivity, i.e. essentially no discrimination against immunoglobulin isotypes.